If you are on any previous tariffs and are given a text allowance, i.e. 500 texts on all of the iPhone tariffs then you will continue to receive your 4-1 on both international and MMS services.
At the point of your next upgrade you will lose that, along with your free voicemail calls.
O2 do offer a 500 text bolt on for £7.50 which includes the 4-1 deal, however I'm not 100% sure if it can be added to the new tariffs or not it's something I'll have a look into when I get the chance.